Hyunsik Jeong

Infosec Researcher

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I started my information security study from the university club called PLUS. I mainly focused on reverse engineering and cryptography while playing CTFs with PLUS, and achieved a lot of results including being the finalist of DEF CON CTF 4 years in a row. After graduation, I joined the graduate school of information security in KAIST, and wrote the master thesis about Qualcomm Hexagon emulators/decompilers analysis. Now, I work in S2W as a researcher, and play CTFs with perfect blue.


Work Experience

Researcher

S2W | Jan 2022 - Present

  • Ransomware research
  • Cryptographic primitives analysis
  • Offensive research

Software Engineer

Kodebox | Oct 2018 - Dec 2019

  • Mainly developed the blockchain called CodeChain (Link) in Rust
  • Developed blockchain node APIs in TypeScript
  • Studied various cryptographic methods used in blockchain technologies

Research Intern

Netmarble | Jun 2018 - Aug 2018

  • Interned at Netmarble AI Revolution Center (NARC)
  • Studied reinforcement learning algorithms, including TRPO & PPO

Projects

Analysis of the Correctness of Qualcomm Hexagon Emulators and Decompilers via Differential Testing

Open Source (Link)

For the master thesis. Analyzed Hexagon emulators (hexagon-sim from the Hexagon SDK, QEMU) and a decompiler (binja-hexagon) with the differential testing tool.

Verifiable Gacha System

Open Source (Link)

A class project. Built a gacha platform with a VRF (verifiable random function). Users can fully access the gacha log, including verifiable random values. Still, only the server can generate random values.

Awards

2022

1st place

Plaid CTF
Team: perfect r00t
2022

1st place

Real World CTF
Team: perfect r00t
2021

1st place

CTFtime
Team: perfect blue
2021

Finalist

DEF CON CTF
Team: Perfect ⚔️ Guesser
2021

1st place

Google Capture the Flag
Team: perfect blue
2021

1st place

Plaid CTF
Team: perfect blue
2020

1st place

CTFtime
Team: perfect blue
2020

1st place

ASIS CTF Finals
Team: perfect blue
2020

1st place

HITCON CTF
Team: Perfect ⚔️ Guesser
2020

1st place

Dragon CTF
Team: perfect blue
2020

Finalist

DEF CON CTF
Team: koreanbadass
2019

Finalist

DEF CON CTF
Team: seoulplusbadass
2019

Finalist

0CTF/TCTF
Team: LeaveCat-PLUS
2019

1st place

CODEGATE CTF (University division)
Team: PLUS
2018

Finalist

CODE BLUE CTF
Team: LeaveCat-PLUS
2018

Finalist

Google Capture the Flag
Team: LeaveCat-PLUS
2018

Finalist

DEF CON CTF
Team: KaisHack PLUS GoN
2017

Finalist

HITCON CTF
Team: LeaveCat-PLUS
2017

Finalist

DEF CON CTF
Team: hacking4danbi
2017

26th place

ACM-ICPC Asia Daejeon Regional
Team: Master Spark
2016

10th place

ACM-ICPC Asia Daejeon Regional
Team: Master Spark
2014

Gold prize

Korean Olympiad in Informatics
Team: (None)

Written Challenges

pbctf

2021
Alkaloid stream, Steroid stream, GoodHash,
Yet Another PRNG, Yet Another RSA, Binary Tree (Link)
2020
RGNN, Special Gift, Special Gift Revenge, LeaK, Find rbtree (Link)

CODEGATE CTF

2022
[Quals] Happy S-box, Very Long Flag Validator

Cyber Operation Challenge (사이버작전 경연대회)

2021
printf
2020
Empty File, The Secret Recipe, Moving, Chemical Encryptor, Rusty Pick

POSTECH Programming Competition (PPC)

2019
C - Heights | F - Linear-Feedback Shift Register | I - Kaka & Bebe (Link)
2018
A - Caesar Cipher | G - Turf Wars | I - Line of Bentham (Link)